2011 MCS, 42,000 +/- miles.

So a week ago I had my Mini at the dealer because I had some coolant that leaked on the garage floor. The Mini dealer pressure checked it 3 times, and drove it twice and got it up to operating temperature, and they couldn't find a leak. Today I am driving home from lunch with the in-laws and I get the yellow, half solid, half outlined check engine light. I checked for a code with my code reader, and I get a P0012.

Any ideas? Related to the mystery coolant leak?

It was running fine at the time the light showed up. Oil level is fine, coolant level appears fine in the overflow tank.